Successful development of a vaccine against HIV will likely require the induction of both antibody and/or cellular immune responses sufficient to prevent infection or disease respectively following infectious challenge. While the induction of antibody responses for a variety of other infectious pathogens is readily achieved by a variety of vaccine formulations, live attenuated, recombinant viral vaccines or plasmid DNA vaccines only induce the induction of long-lived cellular immune responses, particularly CD8+ T cell responses. Moreover, since live attenuated HIV vaccines might be precluded from use due to safety concerns and DNA vaccines at present only induce modest CD8+ T cell responses in humans, there is an urgent need to develop ways to enhance the generation and maintenance of CD8+ T cell responses in humans in following immunization. This study focuses on how to optimize the magnitude and duration of CD8+ T cell responses following vaccination in rodents and primates using a variety of vaccine formulations.[unreadable] [unreadable] [unreadable] The data obtained over this past year have shown the following;[unreadable] [unreadable] 1. Prime-boost immunization with SIV Gag protein and TLR 3 or 7/8 ligands elicit potent T cell responses in non-human primates. Such responses were noted in both peripheral blood mononuclear cells and were much higher in the broncheoalveolar lavage. Upon boosting with rAd-5 SIV , CD8+ T cell responses were further enhanced. Animals were challenged with SIV Mac 251.[unreadable] These results show that a heterologous prime-boost immunization regimen using a protein and TLR ligand followed by rAd-5 induces potent T cell immunity.